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Block 4 > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

What is innate immunity?

A

Body’s first line defence against pathogens

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2
Q

Tell me about the physical barriers in the human body

A

Innate immunity
Everything on the surface (tight junction, eyelids/lashes, epithelial cells, cilia, and mucous membrane)

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3
Q

Tell me about the biological barriers in the body

A

Innate immunity

Chemical/organismal

Bacteria, saliva, urine, tears, stomach acid, anti-microbial peptides (alpha and beta defensins in bacterial cell membranes)

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4
Q

What is different in the lymphatic system than the cardiovascular system?

A

Lymphatic vessels carry lymph
Not closed

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5
Q

Where are lymphocytes concentrated?
List lymphatic tissues

A

Lymph nodes
Lymphatic tissues - spleen, thymus, tonsils, adenoid, appendix, Peyer’s patches
Allows them to intercept microbes before they enter circulation

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6
Q

What is the function of lymph nodes?

A

Exchange lymphocytes with the lymph
Intercept microbes before they enter circulation

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7
Q

What is the function of appendix lymphoid tissue?

A

Make antibodies and sensitize T cells (released into lymph)

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8
Q

What is the lymphoid function of the spleen?

A
  • Exchange lymphocytes with blood
  • Lymphocytes make antibodies and sensitize T-cells
  • Macrophages remove microbes and debris
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9
Q

What is the lymphoid function of the thymus?

A
  • Maturation site for T lymphocytes
  • Secretes thymosin
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10
Q

What cells are involved in innate immunity?

A
  • Mononuclear phagocytes (macrophages, dendritic cells, and monocytes)
  • Natural killer cells
  • Mast cells
  • Granulocytes (basophils, eosinophils, and neutrophils)
  • Complement proteins
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11
Q

What are characteristic of the innate system cells?

A
  • Highly phagocytic
  • Myeloid lineage
  • Respond within minutes/hrs of recognizing pathogens
  • Short-lived
  • Rapid response
  • Non-specific
  • No memory
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12
Q

What allows lineage tracing of myeloid cells?

A

Cells differentiate in tissues at different times

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13
Q

What receptors allow innate immune cells to recognize a pathogen?

A

Pattern Recognition Receptors (PRRs)
4 major types

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14
Q

What are the 4 major types of PRRs?

A
  • Toll-like Receptors (TLRs)
  • NOD-like Receptors (NLRs)
  • C-type lectin receptors (CLRs)
  • RIG-1 like receptors (RLRs)
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15
Q

How do PRRs work?

A

Recognize Pathogen-Associated Molecular Patterns (PAMPs)

PAMPs - proteins, peptides, carbs, nucleic acids on pathogen surface that the innate immune cells react to

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16
Q

Tell me about TLRs

A

Toll-like Receptors
- Transmembrane proteins in plasma membrane or endosomes
- Broad range of specificities
- Activates MAP kinase, NFkBm and IRF pathways

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17
Q

Tell me about NLRs

A

NOD-like Receptors
- Cytoplasmic receptors w many subfamilies
- recognize bacterial, viral, parasitic, and fungal PAMPs
- NOD1 and NOD2 recognize bacterial peptidoglycan

18
Q

How do NLRs recognize viral and bacterial DNA?

A
  • AIM2 detects viral and bacterial DNA
  • Forms signalling complexes called inflammasomes
  • Activates caspase-1-mediated processing and IL-1B and IL-18
19
Q

Tell me about CLRs

A

C-type lectin receptors
- Transmembrane proteins in plasma membrane
- Recognize glycans on bacteria and fungal walls
- Activates kinase syk and CARD9/MALT1/Bcl-10 adapter complex

20
Q

Tell me about RLRs

A

RIG-1 like receptors
- Cytoplasmic receptors of viral DNA
- Signal via mitochondrial adaptor protein MAVS
- Trigger antiviral responses inc type I interferon production

21
Q

Which PRRs are transmembrane?

A

CLR - C-type lectin receptors
TLR - Toll-like receptors

22
Q

What PRRs are cytoplasmic?

A

NLRs and RLRs

23
Q

Do cells only have 1 type of PRR?

A

No, they usually have multiple working at the same time
- There are PRR that are specific for certain PAMPs and DAMPs

24
Q

What is a consequence of PAMP-PRR interaction?

A

Interaction leads to downstream signalling –> inflammatory signals and get the innate immune cell ready to communicate with cells of the adaptive immune system

25
Q

Tell me about DAMPs

A

Damage-Associted Molecular Proteins
- Inc DNA, mtDNA, ATP, ADP and other components that are normally inside the cell
- PRR will respond to these molecules
- Released when a cell has been dmged

26
Q

How do innate immune cells get rid of pathogens?
Give steps

A

Phagocytosis
- Starts PRR and PAMP interact (opsinization)
- actin rearrangement of immune cell to surround pathogen —> phagosome
- Lysosomes fuse phagosome —> digestion
- Immune cells can also present the phagosome to the adaptive immune system cells via MHC

27
Q

What are opsonins?

A

Proteins that bind to foreign bodies to make it easier for phagocytes to stick to the pathogen

Phagocytes have receptors that bind to opsonins

28
Q

What are the main phagocytic cells?

A
  • Macrophages
  • Neutrophils
  • Dendritic cells
29
Q

What is the most resilient phagocyte?

A

Macrophage

30
Q

What are the cardinal signs of inflammation?

A
  • Heat
  • Redness
  • Swelling
  • Pain
  • Loss of function
    Mediated by increase vascular diameter
31
Q

What is inflammation?

A

Altered blood flow, increased immune cells, foreign antigen removal, and healing of dmged tissue

  • Response consisting of vasodilation (arteriole and caps)
  • Increase cap permeability from histamine
  • Edema
32
Q

Do pathogens always cause disease?

A

No; most people with a healthy immune system do not get a disease from encountering a pathogen

33
Q

What is the function of coughing/sneezing?

A

Helps expel foreign particles from the respiratory tract

34
Q

What causes immune cells to move to a site of infection or injury?

A

Chemotactic signals

35
Q

What cells are the bridge between the innate and adaptive immune system?

A
  • γ δ T-cells
  • natural killer T cells
36
Q

Do immune cells only respond to infection?

A

No, they will also respond to injury by recognizing DAMPs

37
Q

These cells have different names depending on the tissue they’re residing. Their function stays the same in all tissues

A

Macrophages

38
Q

Does the speed of the innate immune response get faster with subsequent exposure to the same antigen?

A

No, takes the same time regardless of previous exposure

39
Q

What is opsonization?

A

Flagging of foreign bodies to make phagocytosis easier for phagocytic cells

  • PRRs on phagocytic cells recognize opsonins and engulf the antigen
40
Q

How do immune cells migrate from the blood vessel into tissue?

A
  • Endothelial activation local cells release inflammatory signals —> increased adhesion molecules (selectin)
  • Rolling immune cells stick and roll along vessel lumen
  • Activation chemokines bind to immune cell —> integrin activation on cell —> affinity for endothelial adhesion molecules
  • Firm adhesion intergrins bind —> rolling stops and cell anchors to vessel wall
  • Migration squeezes through tight junctions via actin rearrangement then moves to where chemokines are strongest

Block 4 (6 decks)

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